Prostate cancer (PC) remains a leading cause of morbidity and mortality among men worldwide, highlighting the need for novel therapeutic strategies. Our study investigates the therapeutic potential of targeting the heme degradation pathway through heme oxygenase-1 (HO-1) inhibition in PC. Using both in vitro and in vivo models, we explored the effects of combining HO-1 inhibition with chemotherapy, represented by docetaxel (Doc), on tumor growth and immune infiltration. In vitro experiments demonstrated that HO-1 inhibition, as well as HO-1 knockout (KO), significantly reduced tumor cell proliferation and enhanced chemosensitivity in RM-1 cells. Additionally, U937 cells co-cultured with HO-1 KO cells shifted cell polarization toward an M1 phenotype. In vivo, the combined treatment of the HO-1 inhibitor, tin protoporphyrin (SnPP), with Doc significantly enhanced anti-tumor efficacy in mouse models compared to chemotherapy or SnPP alone. This combination therapy not only reduced Ki67 expression and increased CC3 expression in tumor tissues but also shifted macrophage polarization toward an M1 phenotype and enhanced CD4